From the FAA airplane flying handbook:
A sideslip is entered by lowering a wing and applying just enough opposite rudder to prevent a turn.
From the FAA airplane flying handbook:
In a forward slip, ... the wing on one side is lowered by use of the ailerons. Simultaneously, sufficient opposite rudder is used to yaw the airplane’s nose in the opposite direction such that the airplane remains on its original flightpath.
Technically, there is no difference between a forward slip and a sideslip, in that they both require crossed controls. However, the
purpose of each is different, in that the intention of the forward slip is to lose altitude without increasing airspeed while maintaining ground track and flightpath, even though the nose of the aircraft will no longer point in the direction of the flightpath, while the intention of the sideslip is to maintain aircraft heading and flight path, relying on a countering crosswind to maintain ground track - essential in landing to ensure that the nose is pointing straight down the runway, i.e. aircraft heading is aligned with flightpath to avoid drift and lateral loading on the undercarriage.
This is the "wing down" method of crosswind landing, as opposed to the "crab" method, where there is no crossed control, and the nose is pointed into wind so that the ground track is aligned with the runway - with the nose yawed to align with the runway just before touchdown. I've always been a crab man myself, but I'm a Cancerian, so it was written in the stars.
